Experimental Analysis of Pressure Pulsation Noise Phenomenon in a CNG-Powered Passenger Vehicle

Compressed Natural Gas (CNG) engines are emerging as a viable alternative to gasoline and diesel in heavy commercial and passenger transport worldwide. They offer reduced CO₂ emissions and support energy independence in regions rich in natural gas. In India, enhanced CNG infrastructure and strict emission regulations have driven OEMs to develop CNG vehicles across all segments. Moreover, from a noise and vibration standpoint, CNG vehicles are expected to deliver cabin refinement comparable to that of their fossil fuel counterparts.

However, one of the major challenges associated with CNG vehicles is the excitation due to additional components like CNG Pressure Regulator, Injector et al. The operational metallic/pulsation noises are generally higher as compared to liquid fuels like gasoline due to dry nature of the CNG fuel. This paper describes in detail the pulsation noise phenomena encountered during one of the late-stage vehicle development projects. An experimental root cause analysis methodology was established to identify the structural & cavity resonances phenomena of the CNG Regulator & Low-Pressure gas column along with identification of frequencies of various CNG sub-systems. Studies were carried out to de-couple resonance behavior of the system and improve attachment point stiffness as potential improvement solutions to mitigate this noise. The study also helped to define design guidelines to avoid such issues in future similar development models.